The major objective is to investigate the development of mastery motivation in the first year of life. In a previous study, (Z01 HD 00008-04) three aspects of mastery were distinguished: persistence in problem solving, in practicing emerging sensorimotor skills, and in obtaining feedback from the physical environment. The interrelationships among these components of mastery motivation are being explored, and the origins of mastery and its continuity over time are being studied. The sample includes 75 infants from middle income families. Several methods are being employed--twelve tasks designed to measure mastery motivation; observation of mother-infant and father-infant interaction in the home; Bayley Scales of Infant Development and parent perception of infant temperament. Analyses will focus on continuity in mastery behavior between 6 and 12 months, its relationship to early cognitive development, and the relationship between parent-infant interaction and the development of mastery.